A former defence minister has accused world leaders of concealing the presence of aliens.

Paul Hellyer, who was a Canadian minister from 1963 to 1967, is now urging world powers to release what he believes to be hidden data on UFOs.

'Much of the media won't touch [the documents]', he said during a keynote speech at the Disclosure Canada Tour at the University of Calgary.

'You just have to keep working away and hope that someday you get a critical mass,' he said, according to a report by CTV.

'[The public] will say, in one way or another, "Mr President or Mr Prime Minister we want the truth and we want it now because it affects our lives."'

Hellyer, 91, first went public with his belief in aliens on Earth in 2005, becoming the first high ranking politician to do so.

He claims that the aliens have 'been visiting our planet for thousands of years' and are unimpressed with how we live.

'We spend too much time fighting each other, we spend too much money on military expenditures and not enough on feeding the poor and looking after the homeless and sick,' he said.

Last year, the former Canadian defence minister declared on Russian TV that aliens are walking among us.

But he said they are refusing to share their advanced technologies until we change our polluting and warring ways.

He told Russia Today's program SophieCo there are 80 different species of extra-terrestrials some of whom 'look just like us and they could walk down the street and you wouldn't know if you walked past one.'

In the bizarre interview, Hellyer made a series of pronouncements about aliens which grew increasingly outlandish and sounded closer to the plot of Star Trek.

'We have a long history of UFOs and of course there has been a lot more activity in the last few decades since we invented the atomic bomb,' he said.

'They are very concerned about that and that we might use it again, because the whole cosmos as a unity, and it affects not just us but other people in the cosmos.

'They are very much afraid that we might be stupid enough to start using atomic weapons again.'

However Hellyer told SophieCo that most of the aliens want to help rather than destroy us.

'I would say that nearly all are benign and benevolent and they do want to help us, there may be one or two species which do not,' he said.

Hellyer believes aliens are responsible for some of our modern technology including the microchip, LED light and Kevlar vest, he said.

He says he has never met an alien, but has seen a UFO near his cabin on Ontario's Lake Muskoka.

Hellyer described several types of aliens including 'Tall Whites' who are working with the U.S. air force in Nevada.

'They're able to get away with that; they had a couple of their ladies dressed as nuns go into Las Vegas to shop and they weren't detected,' he claimed.

Another group of aliens are called 'Short Greys' who have very slim arms and legs and are about five feet high with large heads.

A third group are called 'Nordic Blondes' and Hellyer said that if you meet one you'd probably say, 'I wonder if she's from Denmark or somewhere.'